以化學取代調控紅色窄光譜氮化物螢光粉發光強度與波長

Chemical Control of Intensity and Wavelength of Red-emitting Narrowband Nitride Phosphors

孟書怡(Shu-Yi Meng)

指導教授 ： 劉如熹

國立臺灣大學/理學院/化學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201800996

摘要

SrLiAl3N4:Eu2+(SLA)紅色窄光譜氮化物螢光粉，因其優異之結構與光譜性質，被視為最具潛力之紅色螢光粉以應用於白光發光二極體(white light-emitting diodes; WLEDs)裝置中。白光發光二極體之品質與螢光粉之放光效率與光視效能相關，而光視效能與螢光粉之放光位置與半高寬相關。然而，文獻中SLA氮化物螢光粉放光效率尚未達商用標準。此外，以紅色螢光粉而言，獲得較佳光視效能之理想放光位置為620至630 nm間。SLA紅色氮化物螢光粉放光位置位於655 nm，然於此放光位置人眼之感受度較低。為得較佳品質之螢光粉以應用於白光因此，本研究使用助熔劑配合化學取代對SLA螢光粉粉體進行優化與改質。第一部分利用添加助熔劑使SLA螢光粉粉體之結晶性提升，以優化螢光粉之光譜特性，並使其於高溫裝置所產生之色偏移下降。第二部分使用化學取代以Ga3+取代Al3+之方式，藉改變SLA螢光粉主體晶格環境，以嘗試調控其放光位置由655 nm藍移至630 nm，進一步提升其於裝置中之光視效能，提升為SLA之1.25倍，並應用於白光發光二極體。
藉獨特之高壓固態反應法，合成SLA紅色氮化物螢光粉。藉由粉末X光繞射(XRD)對粉體晶格結構進行鑑定，並使用軟體TOPAS對粉體進行結構精修，以探討晶體之晶胞參數變化。使用光激光譜儀量測樣品之光學特性，並藉分析變溫放射光譜以觀測螢光粉於不同溫度環境之光學性質。經分析時間解析光譜與螢光壽命，更深入探討螢光材料之放光中心之配位環境變化。最終，使用紫外-可見-近紅外光譜分析系統以了解其應用於白光發光二極體裝置之可行性。

關鍵字

氮化物螢光粉

並列摘要

The narrowband red-emitting phosphor SrLiAl3N4:Eu2+(SLA) with extraordinary structure and excellent luminous properties is regarded as a prospective red phosphor for white light-emitting diodes(WLEDs). The quality of the white-LED depends on the emission intensity and luminous efficacy of radiation (LER) of the component phosphor, which is, in turn, is related to the emission wavelength, and the bandwidth of the phosphor. As it is now, the emission efficiency of SLA is still not sufficient for the commercial application. Besides, to obtain the optimum luminous efficiency, the emission wavelength of the phosphor should be between 620-630 nm, while the emission wavelength of SLA phosphor is at 655 nm, where the human eyes’ sensitivity is low, and will lead to a decrease in LER. Thus, to obtain the high quality of WLED, improving the emission intensity and blue-shifting the emission wavelength of this phosphor are necessary.
The properties of SLA was optimized by chemical substitution with using Ba3N2 as flux. By the addition of flux, the Morphology of the SLA phosphor was improved by smoother surfaces and larger particle sizes that reflected enhanced luminescence properties and stability in the high-temperature devices. By tuning the environment of the luminescence centers via chemical substitution, where the SLA host was modified by substitution of Ga in the Al site, the emission peak at 655 nm was successfully shifted to 630 nm, and enhanced its LER and efficiency up to 1.25 compared to SLA.
The narrowband red-emitting SLA was prepared by using solid-state reaction under high pressure. The crystal structure information was investigated by X-ray diffractometer and refined by TOPAS. To describe the relationship between the crystal structure and its luminous properties, the photoluminescence and the temperature-dependent photoluminescence properties were analyzed. To investigate the environments of the luminescence centers, time-resolved emission spectra and decay times at low temperature were measured, and the ultra violet-visible-Near Infrared device was used to evaluate the feasibility of the fabrication into WLED device.

並列關鍵字

Nitride Phosphor

參考文獻

(1) Sankaran, S.; Ehsani, R. Introduction to the Electromagnetic Spectrum. Springer. 2014.

(2) Goldstein, E. B.; Brockmole, J. Sensation and Perception. Cengage Learning. 2016.

(3) Barton, H.; Byrne, K. Introduction to Human Vision, Visual Defects & Eye Tests. 2007.

(4) 劉偉仁 LED螢光粉技術. 2014.

(5) Ackerman, E. Considerable Material on Vision From a Medical Point of View. Biophysical Science. Prentice-Hall. 1962.